Relatively new user to Tm1 and I need advise on setting up a cube to cumulate data based on the dimension set up that is pre-existing that I cannot change.

There is already a pre existing formula created that pulls data for the 'Monthly FY Total Data' (by month) consolidation based on data inputs from two other cubes. I am trying to create a formula that would be unique to the 'Monthly Cuml' consolidation that will calculate data by month (at an element level) based on the elements from the 'Monthly FY Total' consolidation. I have tried to create a rule based off of attributes to pull data to take 'Previous Month' and add it to 'Current Month' in order to derive to a total, respectively, with no success.

Here are the current rules created concerning the Monthly Cuml consolidtation

['Cuml Oct']=N: ['Oct']; (which works with no problem, I just do not want add a similar formula 11 more times)

Essentially, I am hoping to create on rule that will calculate the cumulative data as oppose to creating 12 different formulas.

Please see the attachment I have added to this thread to give a better visual representation on what I am trying to calculate.
Everything that is colored in blue-gray is considered a dimension and I am trying to create a formula to solve for yellow/gold.
I also displayed the attributes editor
(**the 'Monthly Cuml' consolidation goes throughout the FY and does not stop at 'APR Cuml')